robot room (the room with the read man) guide: take the clockface. Next open the curtains. go to the present rom and collect the mirror and the spanner. In the past room turn off the drip by using the spanner on the wheel (in the bottom left corner). Put the mirror on the wall and go into the present room were the robot is wating with the portal segment. this is the part i found most difficult hope it helps.
I KNOW! lets stop building hotels and just build massive elevator towers! (ps staff elevators are useful because theyu free upthe lifts that have a max capasity)